Light-emitting diode device and method for manufacturing the same

ABSTRACT

A light-emitting diode (LED) device includes a substrate, an epitaxial layered structure disposed on the substrate, a current-spreading layer disposed on the epitaxial layered structure, a current-blocking unit disposed on the current-spreading layer, and a distributed Bragg reflector. The epitaxial layered structure, the current-spreading layer and the current-blocking unit are covered by the distributed Bragg reflector. One of the current-spreading layer, the current-blocking unit, and a combination thereof has a patterned rough structure. A method for manufacturing the LED device is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a bypass continuation-in-part (CIP) application ofPCT International Application No. PCT/CN2019/072021, filed on Jan. 16,2019, which claims priority of Chinese Invention Patent Application No.201810216614.1, filed on Mar. 16, 2018. The entire content of each ofthe International and Chinese patent applications is incorporated hereinby reference.

FIELD

This disclosure relates to a semiconductor lighting device and a methodfor manufacturing the same, and more particularly to a light-emittingdiode (LED) device and a method for manufacturing the same.

BACKGROUND

A semiconductor lighting device has various advantages, such as longservice life, low energy cost, environmental friendliness, high safety,etc., and its use as a novel and highly efficient solid-state lightsource is deemed promising following the inventions of incandescentlights and fluorescent lights. The rapid increase in the applications ofthe semiconductor lighting device provides great economic and socialbenefits. Therefore, the lighting industry utilizing semiconductorlighting device is deemed as one of the emerging industries in the21^(st) century, and is expected to contribute to the development ofoptoelectronic field within the next few years. A semiconductor lightingdevice, such as a light-emitting diode (LED) device, (i.e., also knownas a fourth-generation light source), is generally made of semiconductormaterials such as gallium nitride (GaN), gallium arsenide (GaAs),gallium phosphide (GaP), gallium arsenide phosphide (GaAsP), etc., andincludes a P-N junction for emitting light, in which electrons diffusefrom an N-region across the p-n junction into a P-region, and holesmigrate from the P-region to the N-region, such that radiativerecombination of the electrons and holes is allowed to proceed so as toemit light. Due to its small size, such LED device has been applied invarious fields such as signal lights, displays, backlight sources,illuminations, and decoration lights for city-viewing.

A conventional flip-chip LED usually includes a distributed Braggreflector that is directly formed on an electrically conductivetransparent layer (e.g., indium tin oxide (ITO) layer), and that usuallyhas a thickness of not less than 3 μm to ensure a reflective propertythereof, which might limit a light extraction efficiency at an interfacebetween the distributed Bragg reflector and the electrically conductivetransparent layer, thereby reducing an overall light extractionefficiency of the conventional LED.

SUMMARY

Therefore, an object of the disclosure is to provide a light-emittingdiode (LED) device and a method for manufacturing the same that canalleviate or eliminate at least one of the drawbacks of the prior art.

According to the disclosure, the LED device includes a substrate, anepitaxial layered structure, a current-spreading layer, acurrent-blocking unit, and a distributed Bragg reflector.

The epitaxial layered structure includes a first-type semiconductorlayer, an active layer, and a second-type semiconductor layer that aresequentially formed on the substrate in such order. The epitaxiallayered structure is formed with an indentation which extends throughthe second-type semiconductor layer and the active layer, and whichterminates at the first-type semiconductor layer to expose a portion ofthe first-type semiconductor layer. The current-spreading layer isdisposed on the epitaxial layered structure opposite to the substrate.The current-blocking unit is disposed on the current-spreading layer.The distributed Bragg reflector covers the epitaxial layered structure,the current-spreading layer, and the current-blocking unit, and extendsinto the indentation of the epitaxial layered structure. One of thecurrent-spreading layer, the current-blocking unit, and a combinationthereof has a patterned rough structure.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the disclosure will become apparent inthe following detailed description of the embodiments with reference tothe accompanying drawings, in which:

FIGS. 1 to 11 are schematic views illustrating consecutive steps of amethod for manufacturing a first embodiment of a light-emitting diode(LED) device according to the disclosure, in which FIG. 7 is a partiallyenlarged view of FIG. 6 showing hemispherical protrusions of a patternedrough structure;

FIG. 12 is a cross-sectional schematic view illustrating conicalprotrusions of a patterned rough structure in a second embodiment of theLED device; and

FIG. 13 is a cross-sectional schematic view illustrating frustoconicalprotrusions of a patterned rough structure in a third embodiment of theLED device.

DETAILED DESCRIPTION

Before the disclosure is described in greater detail, it should be notedthat where considered appropriate, reference numerals have been repeatedamong the figures to indicate corresponding or analogous elements, whichmay optionally have similar characteristics.

Referring to FIG. 11, a first embodiment of a light-emitting diode (LED)device according to the disclosure includes a substrate 101, anepitaxial layered structure, a current-spreading layer 107, acurrent-blocking unit, a distributed Bragg reflector 110, a P-typeelectrode unit, and an N-type electrode 114.

The substrate 101 may be one of a flat sapphire substrate, a patternedsapphire substrate, a silicon substrate, a silicon carbide substrate, agallium nitride (GaN) substrate, and a gallium arsenide (GaAs)substrate. In this embodiment, the substrate 101 is a patterned sapphiresubstrate.

The epitaxial layered structure includes a first-type semiconductorlayer 102, an active layer 103, and a second-type semiconductor layer104 sequentially formed on the substrate 101 in such order.

The term “first-type” refers to being doped with a first type dopant,and the term “second-type” refers to being doped with a second typedopant that is opposite in conductivity to the first type dopant. Forinstance, the first type dopant may be an n-type dopant, and the secondtype dopant may be a p-type dopant, and vice versa.

In this embodiment, the first-type semiconductor layer 102 is an N-typesemiconductor layer made of GaN, the active layer is made of a GaN-basedmaterial, and the second-type semiconductor layer 104 is a P-typesemiconductor layer made of GaN. It should be noted that the materialsfor making the first-type semiconductor layer 102, the active layer 103,and the second-type semiconductor layer 104 are not limited to thosedisclosed herein, and may be modified based on practical requirements.

The epitaxial layered structure is formed with at least one indentation105 (not shown in FIG. 11) which extends through the second-typesemiconductor layer 103 and the active layer 103, and which terminatesat the first-type semiconductor layer 102 to expose a portion of thefirst-type semiconductor layer 102.

The current-blocking unit is disposed on the current-spreading layer(107). In this embodiment, the current-blocking unit includes a firstcurrent-blocking layer 106, and a second current-blocking layer 108. Thefirst current-blocking layer 106 is formed on the epitaxial layeredstructure opposite to the substrate 101. The current-spreading layer 107is disposed over the first current-blocking layer 106, and is connectedto the epitaxial layered structure. The second current-blocking layer108 is formed on the current-spreading layer 107 opposite to theepitaxial layered structure, and is formed with an opening to expose aportion of the current-spreading layer 107.

Each of the first and second current-blocking layers 106, 108 may bemade of a material having a relatively low refractive index (e.g.,silicon dioxide), or a material having a relatively high refractiveindex (e.g., titanium dioxide), or may be a distributed Bragg reflector,but is not limited thereto. The current-spreading layer 107 may be, forexample, an electrically conductive transparent layer made of indium tinoxide (ITO), zinc oxide (ZnO) or graphite, but is not limited thereto.

One of the current-blocking unit, the current-spreading layer 107, andcombinations thereof has a patterned rough structure. For example, whenthe patterned rough structure is formed on the current-blocking unit(such as the first current-blocking layer 106), the light-exit surfacearea of the first current-blocking layer 106 may be increased to enhancethe bonding strength between the first current-blocking layer 106 andthe current-spreading layer 107. Similarly, when the patterned roughstructure is formed on the current-spreading layer 107, the light-exitsurface area of the current-spreading layer 107 may be increased toenhance the bonding strength between the current-spreading layer 107 andthe second current-blocking layer 108.

The patterned rough structure may have a plurality of protrusionsprotruding in a direction away from the epitaxial layered structure. Theprotrusions may have any suitable shape and size. In certainembodiments, each of the protrusions is independently selected from ahemispherical protrusion, a conical protrusion, and a frustoconicalprotrusion. A projection of each of the protrusions on the epitaxiallayered structure may have a diameter of not greater than 50 μm. Each ofthe protrusions may have a height of not less than 100 nm. A distancebetween two adjacent ones of the protrusions may be not greater than 20μm.

In this embodiment, the second current-blocking layer 108 of thecurrent-blocking unit has the patterned rough structure which has aplurality of hemispherical protrusions (see FIG. 7). The projection ofeach of the hemispherical protrusions on the epitaxial layered structurehas a diameter of 26 μm, each of the hemispherical protrusions has aheight of 500 nm, and the distance between two adjacent ones of thehemispherical protrusions is 3 μm. With such configuration, thelight-exit surface area of the second current-blocking layer 108 may beincreased by about 100%.

The distributed Bragg reflector 110 covers the epitaxial layeredstructure, the first current-blocking layer 106, the current-spreadinglayer 107, and the second current-spreading layer 108, and extends intothe indentation 105 of the epitaxial layered structure. In certainembodiments, the distributed Bragg reflector 110 has a thickness of notless than 3 μm, so as to exhibit an improved reflectivity.

In this embodiment, the distributed Bragg reflector 110 is formed with afirst through hole 111 and a second through hole 112. The P-typeelectrode unit is formed in the first through hole 111 of thedistributed Bragg reflector and includes a first P-type electrode 109and a second P-type electrode 113. The first P-type electrode 109 isformed in the opening of the second current-blocking layer 108, and iselectrically connected to the current-spreading layer 107. The secondP-type electrode 113 is formed in the first through hole 111 and iselectrically connected to the first P-type electrode 109.

The N-type electrode 114 is formed in the second through hole 112, andis electrically connected to the first-type semiconductor layer 102 ofthe epitaxial layered structure.

With the second current-blocking layer 108 being formed with thepatterned rough structure, an interface between the secondcurrent-blocking layer 108 and the distributed Bragg reflector 110 mayhave an increased surface area, and therefore scattering of lightentering the distributed Bragg reflector 110 may be increased, so as toimprove a light extraction efficiency of the LED device of thisdisclosure. In addition, the patterned rough structure may increase abonding strength between the second current-blocking layer 108 and thedistributed Bragg reflector 110, thereby enhancing the reliability ofthe LED device.

Referring to FIGS. 1 to 11, a method for manufacturing the firstembodiment of the LED device includes the following steps a) to g).

In step a), referring to FIGS. 1 and 2, the epitaxial layered structureis formed on the substrate 101 through, e.g., a metal organic chemicalvapor deposition (MOCVD) process. The epitaxial layered structureincludes the first-type semiconductor layer 102, the active layer 103,and the second-type semiconductor layer 104 that are sequentiallystacked on the substrate 101 in such order.

In step b), referring to FIG. 3, the epitaxial layered structure isetched to form the indentation 105 which extends through the second-typesemiconductor layer 104 and the active layer 103, and which terminatesat the first-type semiconductor layer 102 to expose a portion of thefirst-type semiconductor layer 101. The etching step may be conducted byan inductively coupled plasma (ICP) etching process or a reactive-ionetching (RIE) process.

Step c) is conducted as follows. Specifically, referring to FIG. 4, thefirst current-blocking layer 106 is firstly formed on the epitaxiallayered structure opposite to the substrate 101 through, e.g., a MOCVDprocess and an etching process. The current-blocking layer 106 may befurther formed with the abovementioned patterned rough structure on asurface opposite to the epitaxial layered structure via, e.g.photolithography and dry etching processes (not shown in the figures).

Referring to FIG. 5, the current-spreading layer 107 is then formed overthe first current-blocking layer 106, and is connected to the epitaxiallayered structure through, e.g., a vapor deposition process or asputtering process. The current-spreading layer 107 may be furtherformed with the abovementioned patterned rough structure on a surfaceopposite to the first current-blocking layer 106 via, e.g.photolithography and dry etching processes (not shown in the figures).

Referring to FIG. 6, the second current-blocking layer 108 is formed onthe current-spreading layer 107 opposite to the first current-blockinglayer 106 through, e.g., a vapor deposition process, and then is formedwith the patterned rough structure through, e.g., photolithography anddry etching processes. Referring further to FIG. 7, the patterned roughstructure includes multiple hemispherical protrusions protruding in adirection away from the current-spreading layer 107. The first andsecond current-blocking layers 106, 108 cooperate to form thecurrent-blocking unit.

Afterwards, the second current-blocking layer 108 is subjected to anetching process (such as photolithography and dry etching processes) soas to form the opening to expose a portion of the current-spreadinglayer 107 (see FIG. 8).

In step d), referring to FIG. 9, the distributed Bragg reflector 110 isformed by a chemical vapor deposition process to cover the epitaxiallayered structure, the first current-blocking layer 106, thecurrent-spreading layer 107, and the second current-blocking layer 108,and to extend into the indentation 105 of the epitaxial layeredstructure.

In step e), referring to FIG. 10, the distributed Bragg reflector 110 issubjected to a dry etching process, such that the first through hole Illand the second through hole 112 are formed.

In step f), referring to FIG. 11, the P-type electrode unit is formed inthe first through hole 111 and the N-type electrode 114 is formed in thesecond through hole 112. To be specific, the first P-type electrode 109is formed in the opening of the second current-blocking layer 108 suchthat the first P-type electrode 109 is electrically connected to thecurrent-spreading layer 107, and the second P-type electrode 113 isformed in the first through hole 111 of the distributed Bragg reflector110. The second P-type electrode 113 is electrically connected to thefirst P-type electrode 109, and the N-type electrode 114 is electricallyconnected to the first-type semiconductor layer 102 of the epitaxiallayered structure.

In certain embodiments, after step f), the substrate 101 is furthersubjected to a thinning process, and the resultant LED device may bediced to obtain an independent LED chip.

Referring to FIG. 12, a second embodiment of the LED device according tothe disclosure is substantially similar to the first embodiment exceptthat in the second embodiment, the protrusions of the patterned roughstructure are conical protrusions. As such, the light-exit surface areaof the second current-blocking layer 108 in the second embodiment may beincreased by about 30%. As compared to the first embodiment, the conicalprotrusions can be made by a relatively simple process, and thereforethe manufacturing cost of the second embodiment of the LED device can bereduced.

Referring to FIG. 13, a third embodiment of the LED device according tothe disclosure is substantially similar to the first embodiment exceptthat in the third embodiment, the protrusions of the patterned roughstructure are frustoconical protrusions. As such, the light-exit surfacearea of the second current-blocking layer 108 in the third embodimentmay be increased by 20%. In addition, the frustoconical protrusions haverelatively high mechanical stability, and therefore the third embodimentof the LED device may have a longer service life.

In sum, by formation of the patterned rough structure on at least one ofthe first current-blocking layer 106, the current-spreading layer 107,and the second current-blocking layer 108, the light-exit surface areaof the LED device of this disclosure can be greatly increased, therebyimproving the light extraction efficiency thereof. In addition, thepatterned rough structure can increase a bonding strength between theselayers, thereby enhancing the reliability of the LED device.

In the description above, for the purposes of explanation, numerousspecific details have been set forth in order to provide a thoroughunderstanding of the embodiments. It will be apparent, however, to oneskilled in the art, that one or more other embodiments may be practicedwithout some of these specific details. It should also be appreciatedthat reference throughout this specification to “one embodiment,” “anembodiment,” an embodiment with an indication of an ordinal number andso forth means that a particular feature, structure, or characteristicmay be included in the practice of the disclosure. It should be furtherappreciated that in the description, various features are sometimesgrouped together in a single embodiment, figure, or description thereoffor the purpose of streamlining the disclosure and aiding in theunderstanding of various inventive aspects, and that one or morefeatures or specific details from one embodiment may be practicedtogether with one or more features or specific details from anotherembodiment, where appropriate, in the practice of the disclosure.

While the disclosure has been described in connection with what areconsidered the exemplary embodiments, it is understood that thisdisclosure is not limited to the disclosed embodiments but is intendedto cover various arrangements included within the spirit and scope ofthe broadest interpretation so as to encompass all such modificationsand equivalent arrangements.

What is claimed is:
 1. A light-emitting diode device, comprising: asubstrate; an epitaxial layered structure which includes a first-typesemiconductor layer, an active layer, and a second-type semiconductorlayer sequentially formed on said substrate in such order, and which isformed with an indentation extending through said second-typesemiconductor layer and said active layer and terminating at saidfirst-type semiconductor layer to expose a portion of the first-typesemiconductor layer; a current-spreading layer which is disposed on saidepitaxial layered structure opposite to said substrate; acurrent-blocking unit which is disposed on said current-spreading layer;and a distributed Bragg reflector which covers said epitaxial layeredstructure, said current-spreading layer, and said current-blocking unit,and extends into said indentation of said epitaxial layered structure,wherein one of said current-spreading layer, said current-blocking unit,and a combination thereof has a patterned rough structure.
 2. Thelight-emitting diode device according to claim 1, wherein said patternedrough structure has a plurality of protrusions that protrude in adirection away from said epitaxial layered structure.
 3. Thelight-emitting diode device according to claim 2, wherein each of saidprotrusions is one of a hemispherical protrusion, a conical protrusion,and a frustoconical protrusion.
 4. The light-emitting diode deviceaccording to claim 3, wherein a projection of each of said protrusionson said epitaxial layered structure has a diameter of not greater than50 μm.
 5. The light-emitting diode device according to claim 2, whereineach of said protrusions has a height of not less than 100 nm.
 6. Thelight-emitting diode device according to claim 2, wherein a distancebetween two adjacent ones of said protrusions is not greater than 20 μm.7. The light-emitting diode device according to claim 1, wherein saiddistributed Bragg reflector has a thickness of not less than 3 μm. 8.The light-emitting diode according to claim 1, wherein saidcurrent-blocking unit includes a first current-blocking layer formed onsaid epitaxial layered structure opposite to said substrate, and saidcurrent-spreading layer is disposed over said first current-blockinglayer and is connected to said epitaxial layered structure.
 9. Thelight-emitting diode according to claim 1, wherein said current-blockingunit includes a second current-blocking layer which is formed on saidcurrent-spreading layer opposite to said epitaxial layered structure.10. The light-emitting diode according to claim 1, wherein saiddistributed Bragg reflector is formed with a first through hole and asecond through hole, and said light-emitting diode further comprises aP-type electrode unit and an N-type electrode, said P-type electrodeunit being formed in said first through hole and being electricallyconnected to said current-spreading layer, and said N-type electrodebeing formed in said second through hole and being electricallyconnected to said first-type semiconductor layer of said epitaxiallayered structure.
 11. A method for manufacturing a light-emitting diodedevice, comprising the steps of: a) forming an epitaxial layeredstructure on a substrate, the epitaxial layered structure including afirst-type semiconductor layer, an active layer, and a second-typesemiconductor layer that are sequentially stacked on the substrate insuch order; b) etching the epitaxial layered structure to form anindentation which extends through the second-type semiconductor layerand the active layer, and which terminates at the first-typesemiconductor layer to expose a portion of the first-type semiconductorlayer; c) forming a current-blocking unit and a current-spreading layeron the epitaxial layered structure opposite to the substrate, one of thecurrent-spreading layer, the current-blocking unit, and a combinationthereof being formed with a patterned rough structure; and d) coveringthe epitaxial layered structure, the current-spreading layer, and thecurrent-blocking unit with a distributed Bragg reflector which extendsinto the indentation of the epitaxial layered structure.
 12. The methodaccording to claim 11, wherein the patterned rough structure has aplurality of protrusions that protrude in a direction away from theepitaxial layered structure.
 13. The method according to claim 11,wherein each of the protrusions is one of a hemispherical protrusion, aconical protrusion, and a frustoconical protrusion.
 14. The methodaccording to claim 13, wherein a projection of each of the protrusionson the epitaxial layered structure has a diameter of not greater than 50μm.
 15. The method according to claim 11, wherein each of theprotrusions has a height of not less than 100 nm.
 16. The methodaccording to claim 11, wherein a distance between two adjacent ones ofthe protrusions is not greater than 20 μm.
 17. The method according toclaim 11, wherein in step e), the distributed Bragg reflector has athickness of not less than 3 μm.
 18. The method according to claim 11,wherein in step c), the current-blocking unit includes a firstcurrent-blocking layer formed on the epitaxial layered structureopposite to the substrate, and the current-spreading layer is disposedover the first current-blocking layer and is connected to the epitaxiallayered structure.
 19. The method according to claim 11, wherein in stepc), the current-blocking unit includes a second current-blocking layerwhich is formed on the current-spreading layer opposite to the epitaxiallayered structure.
 20. The method according to claim 11, furthercomprising, a step e) of forming a first through hole and a secondthrough hole in the distributed Bragg reflector, and a step f) offorming a P-type electrode unit in the first through hole and an N-typeelectrode in the second through hole, the P-type electrode unit beingelectrically connected to the current-spreading layer, and the N-typeelectrode being electrically connected to the first-type semiconductorlayer of the epitaxial layered structure.